Abstract: Excess nitrogen in coastal waters is becoming a problem worldwide. Nutrients such as nitrogen come from sewage treatment plants, septic tanks, runoff from fertilizer and animal waste, and the atmosphere. In marine waters, excessive nitrogen affects plant growth and can lead to hypoxia (dissolved oxygen less than 3 ppm) or anoxia (no dissolved oxygen). Both cause fish and shellfish kills. The Environmental Protection Agency, working with local groups, studied two areas in the northeast, Buzzard's Bay, Mass. and Long Island Sound. In both bodies of water, nitrogen levels were high and solutions to point and nonpoint source contributions were sought. Nonpoint sources were more prevalent at the Massachusetts embayment and point sources in the Sound. Mitigating measures ranged from changes in zoning laws that would ease housing density to retrofitting of septic systems and sewage treatment plants to reduce nitrogen discharge. In the future discharge limits may have to be set in the more urbanized Long Island Sound area.